The present invention relates to a paper feed mechanism for a printer provided with, for example, both a tractor feed mechanism and a friction feed mechanism as form feed means.
Conventionally, in a printer provided with both a tractor feed mechanism and a friction feed mechanism, there is provided a mechanism which switches the elastic contact force of a friction roller which elastically contacts a platen according to the paper feed mode. The arrangement is such that elastic contact is made strongly in the case of the friction feed, and elastic contact is made weakly in the case of the tractor feed. For example, in Japanese Patent application No. SHO60-243323 of the present applicant, a construction is disclosed in which the elastic contact force on the platen of the friction roller is changed over by using a cam having a complicated shape, a cam follower which follows this cam, a plurality of levers, and a spring.
In such a conventional mechanism for adjusting the frictional force between the recording paper and the platen according to the tractor feed and the friction feed, respectively, there have been such drawbacks in that the construction is complicated and a long time is required for assembly. In addition, it is difficult to set the frictional force between the recording paper and the platen in respective form feed modes.
It is an object of the present invention to make it easy to set the frictional force between the recording paper and the platen for the tractor feed and the friction feed, and further to improve the assembling characteristics by means of a simple construction.